Popping and stuttering after Efi install and rebuid

15* BTDC static [ initial ] timing will not cause problems.
Thoroughly check the ign system,: cap/rotor for cracks, bad plug leads, sooty spark plugs, etc. Swap the ign coil/box if you have another. Check that you are getting the correct voltage to the coil.

If ok, I would look at the valve train: lifter adjustment/pre-load, burned valves, weak broken v/springs, wiped cam lobes.